Drug pharmacological effects

Pharmacology Drug Distribution which should contain, if known description of drug pharmacologic effects and mechanisms of action in animals and its absorption, distribution, metabolism and excretion. 

Following concurrent administration of two drugs, especially when they are metabolized by the same enzyme in the liver or small intestine, the metabolism of one or both drugs can be inhibited, which may lead to elevated plasma concentrations of the dtug(s), and increased pharmacological effects. The types of enzyme inhibition include reversible inhibition, such as competitive or non-competitive inhibition, and irreversible inhibition, such as mechanism-based inhibition. The clinically important examples of drug interactions involving the inhibition of metabolic enzymes are listed in Table 1 [1,4]. 

Levodopa is a chemical formulation found in plants and animals that is converted into dopamine by nerve cells in the brain. Levodopa does cross die blood-brain barrier, and a small amount is dien converted to dopamine. This allows the drug to have a pharmacologic effect in patients witii Parkinson s disease (Pig. 29-1). Combining levodopa witii another drug (carbidopa) causes more levodopa to reach die brain. When more levodopa is available, the dosage of levodopa may be reduced. Carbidopa has no effect when given alone. Sinemet is a combination of carbidopa and levodopa and is available in several combinations (eg, Sinemet 10/100 has 10 mg of carbidopa and 100 mg of levodopa Sinemet CR is a time-released version of die combined drugs). 

Williams H, Oyefeso A, Ghodse AH Benzodiazepine misuse and dependence among opiate addicts in treatment. It J Psychol Med 13 62-64, 1996 Wiseman SM, Spencer-Peet J Prescribing for alcoholics a survey of drugs taken prior to admission to an alcoholism unit. Practitioner 229 88—89, 1985 Wolf B, Grohmann R, Biber D, et al Benzodiazepine abuse and dependence in psychiatric inpatients. Pharmacopsychiatry 22 54—60, 1989 Wood MR, Kim JJ, Han W, et al Benzodiazepines as potent and selective bradykinin B1 antagonists. J Med Chem 46 1803—1806, 2003 Zawertailo LA, Busto UE, Kaplan HL, et al Comparative abuse liability and pharmacological effects of meprobamate, triazolam, and butabarbital. J Clin Psycho-pharmacol 23 269-280, 2003... 

In conclusion, until now insufficent data have been available to define general rules to predict for which drugs liposome encapsulation will be therapeutically beneficial when applied to the skin. It is too early to draw definite conclusions about the advantage of the vise of liposomes over alternative dermal delivery systems in the therapy for drugs designed to exert a pharmacological effect either locally or systemically. 

There is, however, a unique risk in the bipolar form that antidepressant treatment may trigger a switch into mania. This may occur either as the natural outcome of recovery from depression or as a pharmacological effect of the drug. Particular antidepressants (the selective serotonin reuptake inhibitors) seem less liable to induce the switch into mania than other antidepressants or electroconvulsive therapy. Treatment for mania consists initially of antipsychotic medication, for instance the widely used haloperidol, often combined with other less specific sedative medication such as the benzodiazepines (lorazepam intramuscularly or diazepam orally). The manic state will usually begin to subside within hours and this improvement develops further over the next 2 weeks. If the patient remains disturbed with manic symptoms, additional treatment with a mood stabilizer may help. 

There are pharmacological, social and legal issues to consider in this context of drug dependence and, of course, drug users and abusers vary enormously. A chronic alcoholic is very different from a weekend user of cannabis and any consideration of the topic has to consider legal and social issues as well as pharmacological effects of the drugs. 

The major drug interactions of antidepressants are shown in Table 35—6.9,19,30 Antidepressants cause both pharmacodynamic (e.g., additive pharmacologic effects) and pharmacokinetic (e.g., changes in drug levels) interactions with other medications. 

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